Heatable mass cylinder of die casting machines for plastic masses



oct. 2o, w36. .57 GASR'OW 2,057,945

HEATABLE MASS CYLINDER OF DIE CASTING MACHINES FOR PLASTIC MASSES FiledDec. 6, 1935 2 Sheets-sheet 1 UCI. 20, 1936., 'H GASTRQW 2,05%4

HEATABLE MAss CYLINDER oF DIE CASTING MACHINES FOR PLASTIC MAssEs FiledDeo. .6, 1955 2 Sheets-Sheet 2 Hans an/ra a/u/ yPatented Oct. A2.0,`1936 PATENT ori-ice HEA'rAnE MASS CYLINDER 0F DIE CAST- ING MACHINESFon rLAs'rIc MAssEs Hans Gastrow,-Zerbst in Anhalt, Germany, as-

to Franz Braun Aktiengesellschaft,

` signor Zerbst, Germany 'Application December 6, 1933, Serial No.701.230 In Germany December 10, 1932 6 Claims. (Cl. 1li-4.2)

The invention relates to apparatus for die casting plastic materials,especially artificial resins, formed by heating a pulveruient initialsubstance and more-particularly to the type of die casting machines inwhich a solid cylindric piston moves in a cylinder which it can occupycompletely, and feeds the powder into an adjacent chamber in which it isbrought into the plastic or liquid condition, by external heating, whileat the same time l0 an equal amount of the plastic or liqueiled materialis injected through a nozzle at the other end of the chamber into thedie casting mold.

It is a well-known fact that the friction of the powdered material isexcessively high within the cylinder and chamber, and thus extremelyhigh pressures are required for forcing the cold material into thechamber and for injecting the liquefied material at the same time intothe die casting mold. These conditions become the more difficult, thesmaller the diameter of the cylinders are and the smaller pistons are,since the area of the wall diminishes'linearly as the diameter while thevolume conveyed varies as the square or the same diameter. The adversefrictional -2 resistance lthus grows very sensibly when the cylinderdiameter is reduced. As the diameter must be kept comparatively smallowing to the mass having to be heated up rather quickly and the low heatconductivity thereof, it has l3u been suggested to use annular cylinderswhich, it

is true, improve the heating conditions for the mass but do not accountfor the friction resistance. Moreover the annular cross section of themass cylinder results in diillculties as to the 35 feed of the material.I

It is an object of the presentinvention to substantially reduce thefriction resistance of the material not yet brought into the plasticcondition. To this end the walls of the heating chamber 0 are madegradually enlarging in the feeding di rection from the plane of the endof the working stroke of the piston, and then convergent towards Athenozzle orifice. With this arrangement the enlarged portion is heatedfrom the outside either 45 directly or by means oi an interposedjacketfilled with a heating liquid. of the piston stroke the chamber graduallydiverges any jamming of still unliquefiable material is avoidedandconsequently the friction resist- 50 ance is` extremely reduced.

The accompanying drawings diagrammatically show several embodiments ofthe invention in Figs. l to 6 wh'ileV a practical instance of executionis represented by Fig. '7. Particularlyl 55 Fig. 1 shows a coaxiallyarranged cylinder and As starting from the end heating chamber theinternal space of which is adapted to be completely filled with the massto f be worked.

Fig. 2 shows an embodiment in which the internal walls of the heatingchamber-gradually 5 diverge as far as the nozzle base and houses a corewhich thermally communicates by ribs with the heated wall oi thechamber.

Fig. 3 snows a. section on une III- III of Fig. a.

Fig. 4 shows an embodiment similar -to Figs. 2.10

and 3 but the central core is replaced by ribs integral with andradially extending from the chamber wail, which ribs leave a free spacealong the center line as is obvious from Fig. 5 which is a section online V- V of Fig. 4'. 15

Fig. 6 shows another embodiment in which the internal core of theenlarged portion of the heating chamber is designed as a hollow annularbody provided with a cylindric Vpassage of constant diameter so that themass pressed through the 20 chamber is divided into a solid cylindricportion and a portion of annular cross section enclosing the first namedportion. The said hollow core is provided with a separate electricheating appliance and radial ribs thermally connect. it to the wall ofthe chamber.

Fig. '1 shows a practical form of execution in which the divergentportion of the heating chamber is provided with a core diverging in thesame direction and which at the place ofthe largest diameter isconnected to the chamber wall by several short ribs. While the diameterof. the internal core increases in the same direction as that ofthechamber wall, the gradual increase of the two diameters concerned is soproportioned that the gap left between the core and the said outsidewall gradually diminishes in width from' the inlet opening for theplastic mass towards the nozzle so that the thickness of the layer ofthe, said mass correspondingly decreases down to a 40 minimum amount. tY

In the drawings. l designs the cylinder in Y which a solid cylindricpiston 2 reciprocates in order to push into the heating chamber lpowdered material dropping from thefunnel tinto the said cylinder. Thegradually enlarging internal space of the heating chamber merges into anozzle body 5 the diameter of which gradually' decreases towards thenozzle oriiice 8, while a cock Ba is provided for closing this orice.About the chamber is disposed heat insulation 'l and an electricallyheated jacket 8. The embodiments shown by Figs. 2, 3, 4, and 5 areprovided, between'the heating appliance and the chamber. with a chamber9 containing a liquid, such as 55 oil or the like, uniformly heated bythe electric heaters and intended for uniformly transmitting its heat tothe wall of the chamber. 'I'he ribs I0 transmit heat from the Jacket asquickly and as. deeply as possible to the interior portion of the massto be heated. The central core ll connects these heating ribs with oneanother in the embodiment according to Figs. 2 and 3. In the embodimentshown by Fig. 6 this central core l2 is hollow and has an annular crosssection and a separate electric heater i3 in its wall. In the embodimentrepresented by Fig. 7 the central core Il is of double-conical shape andis so dimensioned that starting from the point where the mass enters theheating chamber the width of the gap between this core and the outsidewall oi the cylinder gradually decreases so that at the largest diameterthereof the layer of the mass shows the minimum thickness.

What I claim as my invention, and desire to secure by Letters Patent,is-

1. Apparatus for die, casting plastic materials formed by heating apulveruient initial substance comprising a cylinder, means for feedingthe substance thereinto, a piston movable in the cylinder, a chamberadjoining said cylinder, and heating means associated with the chamberfor converting into a plastic condition the substance forced thereintoby the piston, the walls of the heating chambery diverglng graduallyfrom their junction with those of the cylinder to reduce the frictlcnalresistance of the substance which is not yet in a plastic condition andthen converging sharply to a nozzle orifice. A

2. Apparatus for die casting plastic materials formed by heating apulveruient initial substance comprising a cylinder, means for feedingthe substance thereinto, a piston movable in the cylin- 4into by thepiston, the walls of the heating chamber diverging gradually from theirjunction with those of the cylinder to reduce the frictlcnal resistanceof the substance which is not yet in a plastic condition and thenconverging sharply v to a nozzle orifice.

3. Apparatus for die casting plastic materials formed by heating apulveruient initial substance comprising a cylinder, means for feedingthe substance thereinto, a piston movable in the cylinder, a chamberadjoining said cylinder, a core in the chamber, and heating meansassociated with the chamber for converting into a plastic condition thesubstance forced thereinto by the piston, the walls of the heatingchamber diverging gradually from their junction with those of thecylinder to reduce the frictlcnal resistance of the substance which isnot yet in a plastic condition and then converging sharply to a nozzleorifice.

4. Apparatus according to claim 3, in which heating means are providedin the core.

5. Apparatus according to claim 3, in which the cross-section of thechamber and the crosssection of the core gradually increase towards thenozzle, the width of the space between the chamber wall and the coregradually decreasing to the end of the divergence while the crosssectionof the approach to the nozzle orifice decreases up to said orifice.

6. Apparatus for die casting plastic materials according to claim 3, inwhich the core is annular.

HANS GASTROW.

